Coating composition of polyvinyl acetate, werner complex, and quaternary ammonium compound, and paper coated therewith



May 1, 1962 E. c. JENNINGS ET AL 3 3 COATING COMPOSITION OF POLYVINYL ACETATE, WERNER COMPLEX, AND QUATERNARY AMMONIUM COMPOUND, AND PAPER COATED THEREWITH Filed May 21, 1959 2 Sheets-Sheet 1 l8 IO 23 17 8 o o o \E 0&9 0 m2 0 14 16 022 2 O IO [5 2O AVERAGE HUM/D BLOCK/N6 FORCE (GRAMS) NUMBER OF CARBON ATOMS /N THE LONGEST C4RBON CHA/N ON THE OUA TE RNA/P) AMMON/UM COMPOUND.

i u 1 g 300 f/CLZ 1 g I 3 20o 9| In E [00 Lu Q :6 El \Q e. o- 1 1 1 0.20 lo 20 INVENTORS COMPOUND WERNER TYP COMPLEX. MONROE- F 5M/ MOLE RAT/O OF QUA TERA/Aky AMMON/UM EDMRD ggf ATTORNEYS May 1, 1962 Filed May 21, 1959 AVERAGE HUM/D BLOCK/N6 FORCE (GRAMS) E. c. JENNINGS ET AL 3,032,523 COATING COMPOSITION OF POLYVINYL ACETATE, WERNER COMPLEX, AND QUATERNARY AMMONIUM COMPOUND, AND PAPER COATED THEREWITH 2 Sheets-Sheet 2 300- I l QUATERNAR) AMMON/UM COMPOUND MOLE RAT/O WERNER TYPE COMPLEX l I 200- l l 1 l I l IOO- ao- O so- 4o- 20- 9 l I l l l l l l l 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 90 I00 PERCENT WERNER 7YPE COMPLEX (QUATERNARY AMMON/UM COMPOUND PRESENT IN AN AMOUNT SUFF/C/ENT 1o PROV/DE THE MOLE RAT/O OF 1.0 INDICATED ABOVE) INVENTORS EDWARD C. JENNINGS MONROE E SM/T H ATTORNEYS Uited States Patent @fifice 3,032,523, COATING COMPOSITION OF. POLYVINYL ACE-, TATE, WERNER CQMPLEX, AND QUATEBNARY AMMONIUM COMPOUND,,AND PAPER COAT ED THEREWITH EdwardC. Jennings, Antioch, and Monroe F. Smith, Walnut Creek, Calif., assignors towFibreboard Paper. Products Corporation, SanrFrancisco, Caliirlr a .corpor. ration of Delaware FiledM-ay 21, 1959 SerPNo. 814,931

8.Claims. (Cl.260-1-29.6)

This invention relates to water-repellentcoating compositions for paperboard-and the like, and-more-particularly to an improvedmoisture resistant composition comprising polyvinyl acetate, a quaternary ammonium compound and a Werner type-chromium-complex. Such coating compositions do not adhere'to each other even under humid or moist conditions. The tendency of coatings to adhere or stick to each other is known as blocking. This application is a continuation in part of application Serial No. 477,362, filed December 23, 1954, now. aban doned.

Water soluble compounds of-the Werner typein whichtrivalent nuclear chromium atoms are coordinated with carboxylic acido groups are described in United States. Letters Patent No.' 2,273,040, No. 2,359,958; and No. 2,544,666, and-compounds 'o f such character arereferred to herein as. Werner type chromium complexes or as. Werner type complexes. Werner'type complexes have been employed as surface'coatings, both alone andas ad ditives to various coating compositions, to provide in creased water repellentcharacteristics. However, for some purposes, the amount of moisture resistance provided by- Werner type complexes is not-all-that is to be desired;

One use of Werner type-complexes has-been as anadditive to-polyvinyl acetate coatings for paperboard carton blanks in order to reduce blocking ofsuch' coatingswhen the blanks are placed in a stack. This blocking makes it particularly difficult to separate individual blanks from stacks of such blanks by automaticfeeding means whichfeed the blanks'to carton setting up machinery. Although. the Werner. type chromium complexthat has acarboxyliq acido group of at least ten carbon atoms reduces the blocking of polyvinyl ,acetate coatings under warm and ry conditions, considerable blocking is obtained under humid or moist conditions when such a Werner type complex is the only moisture repellent additive incorporated in the coating. Werner type complexes with carboxylic acidogroups having less than ten. carbon atoms are: not generally very eflective moisture repellent; compoundswhen employed alone. It would besadvantagcous; to reduce, the problem of} blocking ofpolyvinykacetate coatings inithe presence. OfJmOisture, since the oil-:and fat. resistant polyvinyl acetate coatings .for paper products, are, otherwise very desirable. for. packaging greasy articles.

In summary, this invention; comprises the provisionof a polyvinyl acetatecoating for paperboard: or the like, which coating has increased; moisture resistance due; to, the incorporation of a quaternary ammonium compound; having a. carbon chain of'at. least aboutsixcarbon atoms in length, together with a water solubleWerner type complex that has a trivalent nuclear chromium atom coordi, nated with a carboxylic acido. group. SuchWerner type, complexes that have carboxylic acido groups of at. least, tencarbon atoms. provide optimum waterrepel-lencychar: acteristics. in the polyvinyl acetate coating composition. However, when a quaternary ammoniumcompound is, em-. ployed in the composition together with the Werner type 3,032,523 Patented May 1, 1962 complex inaccordance withthis invention, the number of carbon atoms on the .carboxylic acido group of the Werner type complex is not critical,'since sufficient water repellency maybe obtained from a long-carbon chain on the .1 quaternary ammonium compounds Either the Werner type complex or the quaternary ammonium compound, or preferablyboth, should have a long a carbon chaiu'for optimum resultsl i The composition of this invention comprising polyvinyl acetate, a quaternaryammonium compound and a Werner type chromium complex is employed with particular ad vantage in thefo'rm .of-an"aqueous emulsion for coating paperboard or the like. Paperboard having such coatings have much less blocking than other polyvinyl acetate coatings, particularly. under conditionsof vmoisture and' high humidity. Consequently, paper products having coatings of polyvinylacetate incorporating the Werner complex and quaternary ammoniumcompound-may be stacked and stored under humidconditions without en countering alblocking problem. The composition hereof is. particularly useful for coating paperboard carbon blanks, but-is also useful for coatingother thinner paper products. For convenience all such paper products are referredrto herein aspaperboard.

Best results are obtained when at least one mol of the quaternary ammonium compound .is includedin the polyvinyl acetate composition for'each mol of the Werner type. chromium complex. Also, quarternary ammonium compounds'having at least one chain of six and preferably more carbon atoms attached to the nitrogen atom are most effective in providing increasedmoisture resistance with the Werner type complex, and thusareemployed in thecomposition.

The combination of a quaternary ammonimurn compound .with a Werner type chromiumcomplex in the polyvinyl acetate composition produces a coating ha'ving greater resistance to moisture than a like coating which includes either of suchcompounds alone without the presenceofthe other. The water resistance provided by the Werner type chromium complex is attributed to the outward orientation of long chain fatty acidgroups in the molecule, and it is believed that the additional water repellentleffectobtained by inclusion of the quaternary ammonium compound is obtainedbecause itmasks the exposedcarbonyloxygen groups of the acid in the Werner type chromium complex, and increases water repellency due to its additionallong carbon chain.

With reference to the. drawings,

FIG. 1 is a graph illustrating the decrease in blocking under humid conditions of paperboard coated-with corn-- positions comprising polyvinyl acetate, quaternary ammoni'um compound, and a Werner type chromium com plex as-the number of carbon atoms in the longest carbonchain on .the nitrogen atom of the quaternary ammonium compound is increased,

BIG. 2 is a graph illustrating the change in blocking force nder hu id dit das Q a rldg d coated wi h, mpa i icas c r uql i yl t te; l aw nary ammonium compound and a Werner type chromium complex as the mol, ratio, ofv quaternary ammonium com pound to. Werner.type chromium complex in the coating composition is. increased.

FIG. 3' is. a v graph illustrating, the change in humid; bl i t Pa erb rdoa ed i a p s ien omprising polyvinyl acetate, quaternary ammonium compound and a Werner. type chromium complex as. the'proportion of Werner typev complex. in the coating composition is varied while the mol ratio of quaternary ammonium compound to Werner type chromium complex is maintained equal to one.

In greater detail, any of the well known water soluble Werner type chromium complexes in which a trivalent nuclear chromium atom is coordinated with a substituted or unsubstituted carboxylic acido group may be employed in the polyvinyl acetate compositions of this invention. Carboxylic acido groups having at least ten carbon atoms should preferably be employed in this invention since they provide the greatest water repellent effect. However, as previously described, carboxylic acido groups having less than ten carbon atoms are suitable for use in conjunction with quaternary ammonium compounds having long carbon chains. Werner type complexes having acyclic acido groups of at least ten carbon atoms and the method of their preparation are described in United States Letters Patent No. 2,273,040, while those having cyclic acido groups are described in United States Letters Patent No. 2,359,858. Also, Werner type complexes having acido groups of less than ten carbon atoms in length are readily prepared, as is well known, in the manner described in the aforementioned patents by employing an organic acid or acid anhydride having a chain length of less than ten carbon atoms. Patent No. 2,544,666 relates to the preparation of such complexes having unsaturated acido groups. A readily available and useful Werner type complex, namely stearato chromic chloride, is sold in an isopropanol solution by E. I. du Pont de Nemours & Company under the name Quilon. Quilon contains 29% to 30% by weight stearato chromic chloride, 65% to 70% by weight isopropanol, and less than 5% water.

An example of a suitable Werner type complex having a carboxylic acido group of less than ten carbon atoms in length is methacrylato chromic chloride sold by E. I. du Pont de Nemours & Co. in an isopropanol solution under the name Volan. This compound has a straight chain length of three carbon atoms attached to the carboxylic acido group of the Werner type complex.

Any quaternary ammonium compound may be employed together with the Werner type complex in accordance with this invention to obtain increased moisture resistance and reduction of blocking of coatings. It is the quaternary ammonium nitrogen which is the essential element in the composition, and the character of the four organic radicals is of no importance or significance in obtaining the desired low blocking polyvinyl acetate coating composition except that at least one of the organic radicals must contain a straight carbon chain at least six carbon atoms in length. Likewise. the nature of the anion on the quaternary ammonium compound is of no importance since the anion plays no part or function in providing the low blocking properties, and thus any anion may be present on the quaternary ammonium compound.

The term quaternary ammonium compound as used herein has well defined meaning, and it is given in Websters New International Dictionary, 2nd edition, as a base or salt which may be regarded as a compound of ammonium in which all four hydrogen atoms are replaced by organic radicals. More particularly in chemical terms, such compounds may be designated by the formula: (R N)+X- in which the Rs are any suitable organic radical, N is nitrogen, and X is any anion. Each of the R groups may be any saturated or unsaturated, unsubstituted or substituted, alkyl or aryl groups, acyclic radicals, cyclic radicals of carbon atoms, cyclic radicals containing nitrogen in the ring such as isoquinolinium, aryl-alkyl combinations in one chain, and radicals containing ether linkages. Even alkyl pyridinium compounds may be used as the quaternary ammonium compound. As mentioned above, at least one of the R groups attached to the nitrogen atom should contain an alkyl or alkylene group having at least one straight chain of approximately six or more carbon atoms, although all of the R groups may be long chain groups. However, more than one long chain of carbon atoms attached to the nitrogen atom produces no additional water repellent effect. Although the alkylol-alkyl derivatives and the alkyl-isoquinolium derivatives of the quaternary ammonium compounds provide low blocking values even under moist conditions when employed with the described Werner type complexes, they have certain properties, such as poor wetting or mottle, which render them less desirable as additives than the quaternary ammonium compounds having alkyl or alkylene groups. Examples of specific quaternary ammonium compounds that may be employed are given in Table I, explained more fully hereinafter, it being understood that of the quaternary ammonium compounds listed therein, those having hydrocarbon chains attached to the nitrogen atom are preferred. Examples of anions X which may be in the quaternary ammonium compound include sulfate, nitrate, iodide, hydroxyl, formate, acetate, phosphate, polyacrylate, alginate, bromide, and chloride. The chlorides are preferred because of their ready availability.

Quaternary ammonium compounds that are either soluble or insoluble in aqueous media are useful for the purposes of this invention. When the quaternary ammonium compound is employed in a coating composition for paperboard which is to contain food products, it is generally desirable to use a water insoluble quaternary ammonium compound in order to insure against the possibility of extraction of the quaternary ammonium compound from the coating into the food.

Water insoluble quaternary ammonium compounds may be prepared from soluble quaternary ammonium compounds either prior to addition of the compound to the coating composition, or in situ after the soluble quaternary ammonium compound has been incorporated in the liquid coating composition. Such insoluble quaternary ammonium compounds are readily prepared by reacting soluble quaternary ammonium compounds with a high molecular weight acid or preferably a polymeric polyacid, such as polyacrylic acid, carboxymethyl cellulose, or polyanhydro-beta-d mannuronic acid, alginic acid, or with the alkali metal and ammonium salts of such acids. Such polymeric polyacids are well known and they are characterized by the following repeating group in which n is at least 2 and is preferably large enough to render the quaternary ammonium compound insoluble. Such polymeric polyacids may also be called synthetic resinous polymers having a plurality of organic acid groups:

f 2CC COOH n The H is hydrogen, C is carbon, and O is oxygen. Hydrogen may be replaced by a cation such as sodium, potassium or ammonium. Regardless of what cation is present, the polymeric polyacid is readily reacted with a quaternary ammonium compound by replacement of the cation with the quaternary radical to form the insoluble quaternary ammonium compound.

Furthermore, it is known that the soluble betaine derivatives of quaternary ammonium salts are nontoxic, and

that such betaine derivatives are natural components of many food-stuffs. Since the betaine derivatives of quaternary ammonium salts also provide resistance to moisture and reduction of humid blocking in accordance with this invention, they may likewise be advantageously employed in coating compositions for paperboard containers used for food products. Betain derivatives of quaternary ammonium salts are .substituted or unsubstituted quaternary ammonium betaines which are inner salts having the formula (R R R N)+(CH COO)- wherein R R and R represent any organic radical. Examples of suitable betaine derivatives are cholesteryl, cetyl and melissyl betaine. quaternary ammonium salts.- Another specific example of' a. water soluble betaine quaternary. am-, monium compound which may be employed as the quaternary ammonium compound isbetaine trimethylglycocoll which has the following structural formula:

HiC-N\ CH3 CH The polyvinyl acetate composition is. most convenientlyapplied as a protective coating for paperboard inthe form of an-aqueous emulsion. The incorporation of a quaternary; ammonium compound, and Werner type complex in polyvinyl acetate emulsions provides a coating having very low blocking. Polyvinyl acetate emulsions are sold by E. I. du Pont de Nemours &'Company under. the trademark Elvacet. The Elvacet compositions contain about 55% by weight of resin solids, and are sold in varying viscosities depending upon the degree-of polymerization desired. Such polyvinyl acetate coatings exhibit considerable blocking under humid conditions, even: when a Werner type complex having a carboxylic. acido group of at least ten carbon atoms is included' alone as the water repellent additive in the coating. The incorporation of a quaternary ammonium compound. in such polyvinyl, acetate coating. compositions along with the Werner type complex produces marked; results in reducing the humid blockingof such coatings. Polyvinyl. alcohol is generally presentinsuch coatings,. and the composition of' this invention likewise has a marked efiectin rendering this compound moisture resistant.

Although plasticizers for. the polyvinyl acetate. need not be present in the composition, it is usually desirable to include any of the well known suitable plasticizers in order to increase flexibility of the coating. Examples of suitable plasticizers are butyl phthalyl butyl glycolate and methyl phthalyl ethyl glycolate.

Also, for many purposes it is desirable to include a pigment in the composition to mask the characteristic green color of the Werner-type complex in which trivalent chromium is corordinated with carboxylic acido groups. Examples of compounds that may be employed for this purpose are titanium dioxide, zinc sulfide, and talc. Titanium dioxide is preferred because of its effectiveness in masking the green color. If the color of the Werner type complex is unobjectionable for the purposes for which the composition is to be employed, thepigment may be omitted.

The addition of even a very small amount. of; quaternary ammonium'compoundto the Werner type complex provides improvedwater repellent characteristics. A mol ratio of quaternary ammonium compound to Werner type complex of as'little as 0.1 results in much greater water repellent characteristicsthan. is obtained with theWerner type complex alone. As the ratio of quaternary ammonium compound to Werner type complex is increased to about 0.25, rapid improvement in moisture resistance is obtained. With furtherincreases in the proportion of quaternary ammonium compound until a mol ratio of 1.0 the improvement in moisture resistance is more gradual. Increasing the proportional amount of quaternary ammonium compound to Werner, type complexto mol ratios greater than 1.0 provides little additional improvement. Consequently, a mol ratio of about 1.0 is preferred for best results. A maximum mol ratio of quaternary ammonium compound to Werner type, complex of 50 should not be exceeded as quaternary in excessof a one. to one mol ratio contributes. nothing, and above 50 to one excessive dilution by the quaternary is obtained. a

Whenthe. quaternary. ammonium comppund, and Werner type complex .is .employed to lower the blocking of polyvinyl acetate coating. compositions, any amount of Werner type complex will reduce blocking asv shown in Table III, explained more fully. hereinafter. Gen-. erally, it is advisable to employ atrl'east about 0.1% by weight Werner type complexbased on the weightof poly, vinyl acetate resin-solids. A rapidreduction of humid blocking is obtained as the amount of Werner type com-v plexv is increased to about 0.5%v or more. by weight, based on the weight of the polyvinyl acetate resin solids. Further increases intheamount of Wernertype complex until'about 2% by weight is reached provides a less rapid reduction in humid blocking, and increasing theamou nt of Werner. type, complex'above 2% byweightprovides little advantage. The greater the amount ofWerner. type complex employed,.the more intense the greencolor-becomes and the more difficulty is encounteredin masking the color.

If a plasticizer is included in thecoating composition, the amount of plasticizer employed. depends uponv the degree oftflexibility desired-in the coating. If-arelatively stiff coating is suitable, very. little plasticizer is needed and the plasticizer may evenbe omitted. More than 10% by weight plasticizer, basedonthe total weight of non-volatile constituents in the coating tendstounduly increase the blocking characteristicsof the coating. Poly? vinyl acetate coating compositionsforpaperboard carton blanks preferably employ'between 2% to.7% by weight plasticizer based on the. total weight of. such nonavolatile constituents.

As previously described, it is not necessary-to include a pigment inthe composition. However, sufficient pigment is employed in thecoating composition of polyvinyl acetate,- quaternary ammonium compound, Werner type complex and plasticizer tomask the green; color of the Werner typecomplex if. the color, is objectionable. No pigment is necessary if the green color is unimportant. From 5% to 15% by weight pigment based ontheweight of non volatile constituents in the coating compositionis usually preferred. Below 5% by weight, of. pigment. may not be sufiicient to mask thegreen color,.and/in coatings for paperboard employed: for food products, it isusually desirable that the'color bemasked. If more than; about 40% by. weightpigmentis, employed, thecojatings tend to. become unduly stiff.

The range ofproportions of the. three essential ingredients in the coating compositionwhichrform the solid coating are as follows in termsof solids presenton the dry basis:

Percentby. W ght Polyvinyl acetate to 99 85 Werner type chromiumcomplex 0.1 to 14.95 Quaternary ammonium compound 0.05 to 14.9

Werner type chromium complex 0.25-to-10 Quaternary ammonium compound 0.1 to 5 Pigment 5 to 15 Suspending agent (any conventional suspending agent such as polyvinyl alcohol) 0.5to 4 Plasticizer 2 to.7

It-is apparent that the'coating iscomposed of amajor proportion of polyvinyl acetate and minor proportions of the remaining components. As previously explained, a satisfactory coating may be prepared with very little Werner type complex and quaternary ammonium compound. Also, the pigment suspending agent and plasticizer may be omitted. Furthermore, an amount of the complex and the quaternary ammonium compound considerably in excess of the range indicated may be employed in preparation of suitable coatings although no appreciable improvement in resistance to moisture is obtained by such procedure. The optimum amount of quaternary ammonium compound to employ is best determined in terms of the mol ratio of quaternary ammonium compound to Werner type chromium complex, since the molecular weight of the quaternary ammonium compound may vary considerably.

The composition comprising polyvinyl acetate, the Werner type complex and the quaternary ammonium compound may be prepared by simply mixing the compounds in water to form an emulsion. The Werner type complex of the character described herein is readily soluble in water. Also, most quaternary ammonium compounds are soluble in water. If a water insoluble quaternary ammonium salt is employed, it may be incorporated in the composition as a dispersion. However, it is usually more convenient to insolubilize a soluble quaternary ammonium compound in situ by adding a polymeric polyacid after the soluble ammonium compound has been mixed with the Werner type complex. Best results are obtained when the composition is permitted to stand for a short period before application so that equilibrium will be reached.

The preparation of a coating composition of polyvinyl acetate having low blocking in accordance with this invention does not present any particular problem. Best results are obtained by first mixing a plasticizer, if any is used, in an aqueous emulsion of polyvinyl acetate to render the final coating flexible. Pigment for masking the green color of the Werner type complex is then preferably added in the form of a water dispersion of the pigment in polyvinyl alcohol, although the pigment may be omitted. A suspension of 20% by weight pigment, by weight polyvinyl alcohol and 75% water is convenient for this purpose. Next, the Werner type chromium complex, which is conveniently dissolved in isopropanol, is incorporated by intermixing it together with the mixture of polyvinyl acetate emulsion composition. Finally, the quaternary ammonium compound is mixed into the composition. If it is desired to insoluhilize the quaternary ammonium compound, this may be accomplished by adding a polymeric polyacid to the emulsion as previously explained. A short period of standing before application, such as one or two hours, provides best results since it permits the components to reach equilibrium.

Water is always included in the liquid compositions of polyvinyl acetate, Werner complex and quaternary ammonium compound so that the compositions may be applied as liquid emulsions. The water is a volatile component which evaporates to leave the remaining solids as a coating when the composition is applied to paperboard or the like. The water is present in the composition in an amount sufiicient to render the composition liquid and readily applied by conventional paperboard coating methods. Regardless of whether the pigment or plasticizer are included in the coating, the amount of water employed based on the total weight of the liquid composi tion is between about 25% and 80% by weight water to between about 20% and 75% by weight of solids in the aqueous emulsion. If more than about 80% water is employed, the final coating becomes too thin. On the other hand if less than about 25% water is included in the liquid emulsion hereof, the composition is too viscous to apply and form a satisfactory coating.

The resultant somewhat viscous liquid coating composition may be applied to paperboard by any conventional coating means such as by the kiss roll method, in which the coating is applied by rollers. Although it is not necessary to heat the coating in order to cure it, best results are obtained when the coated paperboard is dried by passing it through a heated drying tunnel, or when the coating is dried by infra red rays. If no drying means is employed, an unduly long period elapses before the coating is dry enough to permit use or stacking of the paperboard. The liquid composition is applied to paperboard in an amount sufiicient to provide a continuous coating when the water evaporates. Approximately 6 to 8 pounds of the liquid coating composition is preferred to provide a continuous coating for one side of 1000 square feet of paperboard, but a range of between one and 20 pounds may be utilized. This means that at least about 3 to 4 pounds of the dried coating composition is preferred for providing a water resistant coating on paperboard, but a paper product having a dry coating of between about 0.5 and 10 pounds of the composition per 1000 square feet of the product is satisfactory.

The data set forth in all of the following tables were obtained from tests employing bleached kraft paperboard coated with the coating compositions specified. The test for blocking under humid conditions was conducted by stacking specimens of the coated paperboard under a weight so that 4 square inches (2 in. x 2 in.) of the paperboard was subjected to a pressure of 4.2 pounds per square inch. The samples were exposed to a temperature of 73 F. at from to relative humidity for 24 hours. The blocked samples were then conditioned for 4 hours at 73 F. and 50% relative humidity while remaining under the same pressure of 4.2 pounds per square inch. The force in grams required to pull the samples apart was then measured at least ten times for each type of coating. The average force is given in the tables as the average humid blocking force.

The coating compositions tested in the following tables were prepared by mixing a polyvinyl acetate emulsion sold by E. I. du Pont de Nemours & Company under the name Elvacet 81-900 with butyl phthalyl butyl glycolate as a plasticizer. A Water dispersion of titanium dioxide suspended in polyvinyl alcohol was then mixed into the composition. The polyvinyl alcohol used was Elvanol 54-22 sold by E. I. du Pont de Nemours & Company. Next, the Werner type chromium complex was added to the mixture, and finally the quaternary ammonium compound was mixed into the composition. The Werner type complex employed in the tests was the chromium-stearic acid complex sold by E. I. du Pont de Nemours & Company under the name Quilon, which complex is sold in an isopropanol solution as previously explained. The total weight of water in the compositions was 50% by weight.

In Table I, the coating compositions tested contained the following components which were all the same, except that the quaternary ammonium compound was varied to determine the effects of varying the carbon chain length of one of the R groups thereof.

Pcrccnt'py Weightol'Non-volatllc Constituents (not including the weight the quaternary ammonium compound) Pgloyginyl acetate (Elvacet 81-- SU) (ftesin solids in the emul- Werner type chromium complex 2.2 (Weight of actual complex in uilon). the solution).

One mole per mole of Werner type complex.

Quaternary ammonium compound (Listed in Table I).

Tabl I.-

Number Average COIH'. Quaternaryv Ammoni m. of Carbon Hurrid pound Compound Atoms in Blocking No. Longest Force in "R Chain Grams.

Control test Withno quaternary 360 ammonium compound employedinthecorrposition, Tetramethylvammonium bromide. 1 271 Tetraethyl ammoniumbromidern 2 248 ,Plenyltrimethyl ammonium io- 1 171 1 e. letga (ethanol) ammoniumchlo- 2 167 n e. r -mpmnylatnmn um 3 3 mide;

n-tetrabutyl ammonium iodides".-v 4 106 I (Cr-.013 alkyl) trimethyl ammo; 13 Av 22 nium chloride. (C12 alkyl) trimethyl ammoru'um 12 33 chloride. (C -C alkyl) dimethylbenzyl 13 Av. 34 f ammonium chloride.

(Cm alkyll trimethyl ammonium 16 41 chloride. (Cw. alkyl) dimet-hylethyl am: 16 29 monium bromide. (Cir alkyl) trimethyl ammonium 18 34 chloride. 1 Dl-(Qg-ClB .alkyl) dimethyl' am- 13 Av. 32

monium chlori e. Tris (ethanol) (C12 alkyl);ammo- 12 v 4 nium chloride. Ilris (ethanol) (C1 alkyl) am.- 18 3 monium chloride. -do 18 14 Tris. (ethanol) (Cnaiky). am-. 22 46 monium-chloride (Cr-C18 alkyll dimethyl 3,4-dicliilorobenzyl ammonium chlc- 13 Av. 37 r1e.. 19 (Cig alkyl) isoquinolinium bro- 12 2.5

m e.- 20 (Crs-Czn.alkylene) dimethyl ethyl; 18 Av. 16

' ammonium bromide.

(C12 alky aryl) trime hyl ammo. 1 -6 nium chloride. (C22 alkyl) trimethyl ammonium 22 11 hlori e. im alky ime hy mmo- 18 44 nium chloride. 1

Thedatain: Table I is plotted in; the form of agraph in FIG. 1. In FIG; 1 the various quaternary ammonium compo nds re n cat by' h C mp n N ig e in Table; I. The; results ofthese tests indicate; the decr as blockin ob a ne w h q at rn ry mm ium compounds as the carbonchain length of; one of the organic groups-attached to nitrogen in the quaternary ammonium compound is increased: It is apparent that no. significant reduction in blocking occurs with quaternary ammonium" compounds, having attached; carbon chains. of a; length greater; than approximatelysix carbon atoms. The difference between the blocking, of thecontrolcoating which employed a Werner type complex without; the presence of a quaternary ammonium com pound, andythe coatings. in which a v quaternary ammonium compound was incorporated in the coating, indicatesthe importance ofi employing a quaternary ammoniumcompound' in-accordance withthis invention. It is apparent that. the quaternary ammonium compounds hav,- ing atleastone chain, of. approximately six or, more carbonatomsattachedto thenumgen atom are most effective in providing increased moisture. resistance.

Thedata in Table Il illustrates the effect of increasing the mol ratio of quaternary ammonium compound to Werner typechrornium complex in the coating composition. The coating compositions employed were-identical to the compositions of Tabl'e I-with respect to the amount and type of polyvinyl acetate, plasticizer, pigment; suspending agent and Werner type chromium. complex. However, thetype and' amount: of quaternary ammonium compound employed in the composition were varied in order to. ascertain the. reduction in blocking obtained with various; amounts. of quaternary ammonium compound. Eachrof the, following quaternary ammonium compounds, (C -C alkyl) trimethylammonium chloride,

(C7 .all ;yl) 'trimethyl: ammonium; chloride ,..(C alkyl dimet-hyl et-hylo ammonium bromide, and. di- (C -C alkyl) dimethyl ammonium chloride was employed in a coatingat the mol ratiosrindicated in Table II in order to ascertain the reductionin blocking obtained with variousamountsof quaternary ammonium compound. The blocking at each mol ratio with, each quaternary ammonium compound was averaged to provide. the result in the;,table,

Table 11 M01 Ratioof-t Quaternary AmmoniumCompound/ Average Humid Werner Type ChromiumComplex Blocking Force.

in Grams Table IIgand thegraph of the. data in the table plotted in FIG. 2illustratethatreverr-a. small amount of quaternary: ammoniumrcompound. incorporated in the coating results in a marked reduction of humid blocking. It is apparent that .norsigni'ficantimprovement is, obtained by increasingthe. amount of quaternary; ammonium in the coatingcomposition after. a mol rati'oof 1.0 is obtained.

TableIII lists .the variation in humid blocking of polyvinyl: acetate. ,coating; compo sitions; obtained. when the amount of Werner type complex in the polyvinyl acetate coating composition is varied While at the-same time sufiicient quaternary ammonium, compound is maintained in the; composition; to provide: amolv ratio of quaternary ammonium compound to; Werner type chromium complex, equal; to one, The composition of the; polyvinyl aceta-tecoatingis thesame as that employed in Table I except; th at;;the amount of Wernertype complex and quaternary ammonium compound was varied as indicated. Quilon? was again employed as the Wernertype complex-,andj thequaternary ammoniumcompound employed in. the; coating compositions was (C alkyl) trimethyl ammonium; chloride which is-sold by Armour and Company under: the name Arquad 16. The data in Table 1111 is; plotted in the. form of graph in;- FIG. III. It is apparent that the greatest reduction inblocking occurs when;a bout 2%, by weight Werner type complex ispresent in; thecoating-composition based upon. the weight of polyvinyl acetate resin,- solids, and that no appreciable further reduction isobtained by additional increasesin the amountof Wernentype, complex.

Table-III.

Percent'by Average Percent by. weight: Werner type Complex Weight Hum d based on the ,Weight.of-polyvinyl ace- ,Quaternary v Block ng tats resin solids in the composition Ammonium force m Compound Grams 11 acetate emulsion mixture. Next parts by weight Quilon, a solution of a Werner type complex sold by E. I. du Pont de Nemours & Company comprising 30 parts by weight stearato chromic chloride Werner type complex, 65 to 70 parts by weight isopropanol, and less than 5 parts by weight water was incorporated into the polyvinyl acetate coating composition with continued stirring. Finally 1 /2 parts by weight of a solution of 50 parts by weight of (C -C alkyl) trimethyl ammonium chloride in 50 parts isopropanol, a quaternary ammonium compound solution which is sold by Armour and Company under the name Arquad C, was intermixed with the composition to form the emulsion to be applied to the paperboard.

The mixture was then applied to the usual paperboard employed for making carton blanks by the conventional roll coating technique. About 8 pounds of the liquid coating composition was used in coating one side of 1000 square feet of paperboard, with 16 pounds being used for both sides.

The paperboard was then dried by passing through a drying tunnel maintained at about 120 C., with a residence time in the drying tunnel of about one minute.

Coated blanks were then cut from the rolls of coated paperboard and the blanks were then stacked and stored for two weeks under humid conditions. Very little blocking was obtained with the blanks, and they were readily separated from each other by automatic blank feeding means associated with a conventional carton setting up machine. We claim:

1. A liquid coating composition for application to a paper product to provide a solid protective coating therefor that exhibits low blocking under both humid and dry conditions, which liquid coating composition contains water as a volatile component present in an amount to render said composition liquid, and contains as the film forming components in the solid coating in percent by weight based on the weight of said film forming components a mixture of organic compounds which consists essentially of (1) from about 85 to 99.85 percent polyvinyl acetate dispersed in said water, (2) from about 0.1 to 14.95 percent of a water soluble Werner-type chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group, said carboxylic acido group having at least three carbon atoms, and (3) from about 0.05 to 14.9 percent by weight of a quaternary ammonium compound, said quaternary ammonium compound being selected from the group consisting of quaternary ammonium salts and quaternary ammonium bases and being present in an amount to provide a molar ratio of quaternary ammonium compound divided by said Werner-type chromium complex of at least 0.1 and not in excess of 50, and said quaternary ammonium compound having a straight carbon chain of at least six consecutive carbon atoms attached to the nitrogen atom of said compound, said coating composition containing plasticizer for said polyvinyl acetate present in an amount less than percent by weight of nonvolatile constituents in said coating composition.

2. The liquid coating composition of claim 1 in which said quaternary ammonium compound is water insoluble.

3. A liquid coating composition for application to a paper product to provide a solid protective coating therefor that exhibits low blocking under both humid and dry conditions, which liquid coating composition contains between about 25 percent and 80 percent by weight water and between about 20 percent and 75 percent by weight solids, and contains as the film forming components in the solid coating in percent by weight based on the weight of said film forming components a mixture of organic compounds which consist essentially of (1) from about 85 to 99.85 percent polyvinyl acetate dispersed in said water, (2) from about 0.1 to 14.95 percent of a water soluble Werner-type chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group, and (3) from about 0.05 to 14.9 percent by weight of a quaternary ammonium compound, said quaternary ammonium compound being selected from the group consisting of quaternary ammonium salts and quaternary ammonium bases and being present in an amount to provide a molar ratio of quaternary ammonium compound divided by said Werner-type chromium complex of at least 0.1 and not in excess of 50, said quaternary ammonium compound having a straight carbon chain of at least six consecutive carbon atoms attached to the nitrogen atom of said compound, and said carboxylic acido group on said Werner-type chromium complex having at least ten carbon atoms, said coating composition containing plasticizer for said polyvinyl acetate present in an amount less than 10 percent by weight of non-volatile constituents in said coating composition.

4. A liquid coating composition for application to a paper product to provide a solid protective coating therefor that exhibits low blocking under both humid and dry conditions, which liquid coating composition consists essentially of water as a volatile component present in an amount to render said composition liquid, and as components which form the solid coating based on the weight of such components in said composition, from 59 to 91.65 percent by weight polyvinyl acetate dispersed in said water, from 0.25 to 10 percent by weight of a water soluble Werner-type chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group, from 0.1 to 5 percent by weight of a quaternary ammonium compound, from 5 to 15 percent by weight of a pigment, from 2 to 7 percent by weight of a plasticizer for said polyvinyl acetate, and from 0.5 to 4 percent suspending agent for said pigment, said quaternary ammonium compound being selected from the group consisting of quaternary ammonium salts and quaternary ammonium bases and being present in an amount to provide a molar ratio of quaternary ammonium compound divided by said Werner-type chromium complex of at least 0.1 and not in excess of 50, said quaternary ammonium compound having an aliphatic hydrocarbon group containing a straight carbon chain of at least six consecutive carbon atoms attached to the nitrogen atom of said compound, and said carboxylic acido group on said Werner-type chromium complex having at least ten carbon atoms.

5. The liquid coating composition of claim 4 in which the amount of water in said composition is between 25 percent and percent by weight of the composition, and the solids that form said coating comprise between about 20 percent and 75 percent of the weight of said coating composition.

6. A paper product having a solid protective coating thereon that exhibits low blocking values under both humid and dry conditions, which solid coating contains as film forming components in the solid coating a mixture of organic compounds which consists essentially of (1) from about to 99.85 percent polyvinyl acetate, (2) from about 0.1 to 14.95 percent of a water soluble Wernertype chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group, said carboxylic acido group having at least three carbon atoms, and (3) from about 0.05 to 14.9 percent of a quaternary ammonium compound, said quaternary ammonium compound being selected from the group consisting of quaternary ammonium salts and quaternary ammonium bases and being present in an amount to provide a molar ratio of quaternary ammonium compound divided by said Werner-type chromium complex of at least 0.1 and not in excess of 50, and said quaternary ammonium compound having an aliphatic hydrocarbon radical containing a straight carbon chain of at least six consecutive carbon atoms attached to the nitrogen atom of said salt, said coating containing plasticizer for said polyvinyl acetate present in an amount less than 10 percent by weight of solids in said coating.

7. The paper product of claim 6 in which said carboxylic acido group on said Werner type chromium complex has at least ten carbon atoms.

8. A paper product having a solid protective coating thereon that exhibits low blocking values under both humid and dry conditions, which solid coating consists essentially from 59 to 91.65 percent by weight polyvinyl acetate, from 0.25 to 10 percent by weight of a water soluble Werner-type chromium complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group, from 0.1 to 5 percent by weight of a quaternary ammonium compound, from 5 to 15 percent by weight of a pigment, from 2 to 7 percent by weight of a plasticizer for said polyvinyl acetate, and from 0.5 to 4 percent suspending agent for said pigment, said quaternary ammonium compound being selected from the group consisting of quaternary ammonium salts and quaternary ammonium bases and being present in an amount to provide a molar ratio of quaternary ammonium compound divided by said Werner-type chromium complex of at least 0.1 and not in excess of 50, said quaternary ammonium compound having an aliphatic hydrocarbon group containing a straight carbon chain of at least six consecutive carbon atoms attached to the nitrogen atom of said compound, and said carboxylic acido group on said Werner-type chromium complex having at least ten car- 10 bon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 15 2,346,755 Hemming Apr. 18, 1944 2,673,824 Biefeld Mar. 30, 1954 2,733,182 Dalton et a1. Jan. 31, 1956 2,801,189 Collier July 30, 1957 

1. A LIQUID COATING COMPOSITION FOR APPLICATION TO A PAPER PRODUCT TO PROVIDE A SOLID PROTECTIVE COATING THEREFOR THAT EXHABITS LOW BLOCKING UNDER BOTH HUMID AND DRY CONDITIONS, WHICH LIQUID COATING COMPOSITION CONTAINS WATER AS A VOLATILE COMPONENT PRESENT IN AN AMOUNT TO RENDER SAID COMPOSITION LIQUID, AND CONTAINS AS THE FILM FORMING COMPONENTS IN THE SOLID COATING IN PRESENT BY WEIGHT BASED ON THE WEIGHT OF SAID FILM FORMING COMPONENTS A MIXTURE OF ORGANIC COMPOUNDS WHICH CONSISTS ESSENTIALLY OF (1) FROM ABOUT 85 TO 99.85 PERCENT POLYVINYL ACETATE DISPERSED IN SAID WATER, (2) FROM ABOUT 0.1 TO 14.95 PERCENT IN A WATER SOLUBLE WERNER-TYPE CHROMIUM COMPLEX IN WHICH A TRIVALENT NUCLEAR CHROMIUM ATOM IS COORINATED WITH A CARBOXYLIC ACIDO GROUP, SAID CARBOXYLIC ACIDO GROUP HAVING AT LEAST THREE CARBON ATOMS AND (3) FROM ABOUT 0.05 TO 14.9 PERCENT BY WIGHT OF QUARTERNARY AMMONIUM COMPOUND, SAID QUARTERNARY AMMONIUM COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF QUARTERNARY AMMONINUM SALTS AND QUARTERNARY AMMONIUM BASES AND BEING PRESENT IN AN AMOUNT TO PROVIDE A MOLAR RATIO OF QUARTERNARY AMMONIUM COMPOUND DIVIDED BY SAID WERNER-TYPE CHROMIUM COMPLEX OF AT LEAST 0.1 AND NOT IN EXCESS OF 50, AND SAID QUARTERNARY AMMONIUM COMPOUND HAVING A STRAIGHT CARBON CHAIN OF AT LEAST SIX CONSECUTIVE CARBON ATOMS ATTACHED TO THE NITROGEN ATOM OF SAID COMPOUND, SAID COATING COMPOSITION CONTAINING PLASTICIZER FOR SAID POLYVINYL ACETATE PRESENT IN AN AMOUINT LESS THAN 10 PERCENT BYWEIGHT OF NONVOLATILE CONSTITUENTS IN SAID COATING COMPOSITION. 